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Helicoprion is a genus of extinct shark-like [1] eugeneodont fish. Almost all fossil specimens are of spirally arranged clusters of the individuals' teeth, called "tooth whorls", which in life were embedded in the lower jaw. As with most extinct cartilaginous fish, the skeleton is mostly unknown.
According to the fossil record, the divergence of coelacanths, lungfish, and tetrapods is thought to have occurred during the Silurian. [47] Over 100 fossil species of coelacanth have been described. [46] The oldest identified coelacanth fossils are around 420–410 million years old, dating to the early Devonian.
The study of prehistoric fish is called paleoichthyology. A few living forms, such as the coelacanth are also referred to as prehistoric fish, or even living fossils, due to their current rarity and similarity to extinct forms. Fish which have become recently extinct are not usually referred to as prehistoric fish.
Members of the Eugeneodontiformes are further classified into different families, the most well-preserved members that have been discovered are commonly placed within the families Helicoprionidae ("spiral saws"), and Edestidae ("those which devour"), the former containing the genera Helicoprion, Sarcoprion, and Parahelicoprion, and the latter ...
This second use is invalid (as are all subsequent uses) and the name must be replaced. As preoccupied names are not valid generic names, they will also go unitalicized on this list. Nomen dubium (Latin for "dubious name"): A name describing a fossil with no unique diagnostic features. As this can be an extremely subjective and controversial ...
Leedsichthys, a giant Jurassic pachycormid. This list of prehistoric bony fish is an attempt to create a comprehensive listing of all genera from the fossil record that have ever been considered to be bony fish (class Osteichthyes), excluding purely vernacular terms.
Placoderms were among the first jawed fish (their jaws likely evolved from the first pair of gill arches), as well as the first vertebrates to have true teeth. They were also the first fish clade to develop pelvic fins , the second set of paired fins and the homologous precursor to hindlimbs in tetrapods .
A fossil specimen of Onychodus from Western Australia was found with a placoderm fish half its length logged in its throat. [20] [21] This interesting find was described and illustrated by Dr. John A. Long. [4] [19] [21] The pectoral fins were strong enough for the animal to "walk" around the sea floor in search of a hiding place between coral ...